The class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon is known in the art. An early disclosure of such polymers was by Nozaki, e.g., U.S. Pat. No. 3,694,412. The more recent processes for the production of such linear alternating polymers is illustrated by a number of published European Patent applications including 121,965, 181,014, 213,671 and 257,663. These processes typically involve the use of a catalyst compound formed from a compound of palladium, a strong non-hydrohalogenic acid and a bidentate ligand of phosphorus or nitrogen, particularly phosphorus. The resulting polymers, now known as polyketones or polyketone polymers, are relatively high molecular weight materials having established utility as thermoplastic polymers. The polyketones are processed by methods conventional for thermoplastics, e.g., extrusion, injection molding and thermoforming, into a variety of useful shaped articles such as containers for food and drink.
In the production of the linear alternating polymers, the polymerization rate and also the molecular weight of the polymer are important considerations. It would be advantageous to produce polymer at a high polymerization rate. It is also of importance to produce a linear alternating polymer of a relatively high molecular weight because of the particularly useful properties of such products. The polymerization rate and product molecular weight are both influenced by reaction temperature but an increase in reaction temperature which results in a more rapid polymerization rate will generally result in a lower molecular weight. As a result of this inverse relationship, it is often necessary to choose a reaction rate which will produce product of the desired molecular weight and accept whatever polymerization rate results.
When the polymerization process is conducted in a batch type process, the ratio of non-hydrohalogenic acid to palladium is also important. In batchwise operation, it has been found that increases in product molecular weight and also reaction rate are obtained at a given temperature as the molar ratio of the non-hydrohalogenic acid to the palladium is increased up to a value of about 10. Molar ratios below 10 and in some cases below 6 are known, for example, from published European Patent Applications 339,744 and 213,671, but in batchwise operations and provide inferior results. It is on some occasions desirable to conduct the polymerization process in a continuous manner in one reactor or several reactors in series. In a continuous process the reaction conditions are substantially constant and the process is easier to control. A continuous process which employs a molar ratio of non-hydrohalogenic acid to palladium as high as 10 does, however, have some disadvantages. The presence of non-hydrohalogenic acid in the polymer product can lead to discoloration and/or decomposition. While the acid in the polyketone product can be removed or at least reduced in quantity as by water washing, such reduction of acid does require additional process steps. It would be of advantage to provide an improved continuous-type polymerization process which employs a lower acid/palladium molar ratio.